Hi Evgeny,

In our experience, 15um depth causes no problem with proximity
and little problem with optical projection alignment systems at
the line widths you are looking at. If more is needed, Karl Suss
has a LEGO (Large Exposure Gap Optics) system that helps.
You might have problems applying a uniform resist layer by spin
coating, though. Spraying or electrophoretic deposition are good
alternatives. If the whole trench is filled with resist (as is
probable by spin or spray), you need to optimise exposure for
>15um thick resist layer - and you might get reflection effects
at the side walls.
I hope this helps. Contact me if you need more advice. I have no
experience with e-beam exposure, though.

Greetings,
        Frank Berauer
        Senior R&D Engineer
        Hewlett-Packard Singapore


-----Original Message-----
From: Evgeny Gutyrchik [mailto:gutyr@biochem.mpg.de]
Sent: 15 February 2002 21:05
To: mems-talk@memsnet.org
Subject: [mems-talk] E-Beam Lithography


Hi,

I have 8 um width,  15 um deep channels anisotropic etched in SiO2 and want
expose in a positive photoresist 3 to 6 um width lines on the bottom of
this channels. Have anybody ever tried something similar? I have problems
with optical lithography (proximity effects), so am thinking on E-Beam
lithography... Can one positioning a sample in REM without simultaneously
significant exposing the resist? There are different PMMA types (and others
resists?), what would be most suitable? Would it works at all?

Regards,
Evgeny Gutyrchik
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